A convergent pattern of equally spaced black and white lines, used in a television test pattern to indicate resolution.

A piece of resistant material whose two major surfaces make an acute angle.

A waveguide termination consisting of a tapered length of dissipative material introduced into the guide, such as carbon.

In ultrasonic testing, a device which directs waves of ultrasonic energy into the test piece at an angle.

A polyhedron whose base is a rectangle and whose lateral faces consist of two equilateral triangles and two trapezoids.

See <<ridge>>

1. An optical filter in which the transmission decreases continuously or in steps from one end to the other.

2. A refracting prism of very small angle, inserted in an optical train to introduce a bend in the ray path.